Prior art systems for providing ventilation of heading characteristically contain a blower which is mounted on a mining machine. An example of a blower mounted on a mining machine is disclosed in U.S. Pat. No. 3,824,911 (Janelid et al). As disclosed in this patent, the blower sucks fresher air in along one wall and directs the air back out along another wall so that the two air currents are stratified. In a further prior art system, the so-called Automated Extraction System (AES), the air is blown out of the heading by means of collapsible tubing which runs from a blower on a machine to the downstream side of a tunnel with through ventilation.
There are a number of disadvantages to the prior art systems. First, when the electrical power to the machine is cut off for any reason, the blower on the machine stops functioning as well and the heading is then unventilated. Further, when the machine, and hence the blower, is moved out of the heading, the heading will also be unventilated. While both of these problems are currently solved by hanging so-called line curtain, this is a cumbersome and time consuming operation. In addition, hanging line curtain is also not a suitable solution for an automated, high production system. Thus, prior art systems do not provide a reliable and continuously operable system for providing fresher air to a heading. Furthermore, prior art systems do not provide immediate ventilation as soon as the blower on the machine stops blowing.